BN_is_prime_fasttest(), when called with B<do_trial_division == 1>,
first attempts trial division by a number of small primes;
if no divisors are found by this test and B<callback> is not B<NULL>,
B<callback(1, -1, cb_arg)> is called.
If B<do_trial_division == 0>, this test is skipped.
BN_is_prime_fasttest(), when called with B<do_trial_division == 1>,
first attempts trial division by a number of small primes;
if no divisors are found by this test and B<callback> is not B<NULL>,
B<callback(1, -1, cb_arg)> is called.
If B<do_trial_division == 0>, this test is skipped.